State and local lotteries have become important fund raising events for the sponsoring agency. The popularity of lotteries has soared in the 1980's and continues to grow.
Those agencies charged with the administration of lotteries are acutely aware of the need to maintain the integrity of the lottery system from the printing of lottery tickets to the validation of prize winning numbers. Accordingly, much effort has been made to insure that all tickets are authentic. It is generally recognized that in order for a lottery game to be successful, from the point of view of both the purchaser and the sponsor, the lottery ticket must be secure against counterfeiting.
Scratch-off type lottery tickets are those having at least one area overprinted with an opaque latex ink. When the latex ink dries it forms a protective coating that can be scratched off to reveal preprinted indicia indicating whether or not a prize has been won.
In the early 1980's, scratch-off type lottery tickets were printed on a foil-laminated substrate. The reflectance of the substrate made it difficult for counterfeiters to photocopy a winning ticket. Since the foil reflects all wavelengths of the electromagnetic spectrum, a photocopy shows black in the foil area, thus making detection of a counterfeit ticket relatively easy.
In the late 1980's the use of foil laminated substrates was criticized on environmental grounds. The foil is not biodegradable and can not be readily recycled. Accordingly, lottery sponsors have encouraged lottery ticket manufacturers to create an environmentally compatible lottery ticket which can be authenticated with the same degree of assurance as foil laminated tickets. Virgin and preferably recycled paper are preferred substrates for environmentally compatible lottery tickets.
Authentication of a non-foil paper substrate was complicated by the development of high quality color photocopiers which occurred in the late 1980's. Such copiers are capable of duplicating a winning ticket with a high degree of precision even for multicolored lottery tickets. In addition, authentication of valid winning tickets is primarily the responsibility of the lottery ticket retailer. He or she is charged with the responsibility of visually checking the ticket to detect any signs of tampering or duplication. However, retail agents often do not have the time to carefully check winning tickets, particularly during peak sale periods. Furthermore, any equipment which may be required for authentication, such as ultraviolet light is either too time consuming or bulky for convenient use by retail agents.
There have been a variety of efforts proposed to prevent tampering of lottery tickets. One such method has been the use of inks which undergo an irreversible color change when exposed to elevated temperatures. For example, James McCorkle, U.S. Pat. Nos. 4,407,443 and 4,488,646 and Canadian Patent No. 1,158,104 disclose a lottery ticket using a blush coating composition which employs a mass of dispersed light-scattering polymeric particles. The polymeric particles are activated into an irreversible color change when exposed to heat or organic solvents. Lee A. Carrier U.S. Pat. No. 4,120,445 discloses an irreversible color change in the form of a blush-coat type of composition. A first laminate is carried on a paper substrate which includes a radiation-blocking coating as well as irreversible coloring agents which are susceptible to chemical agents or are heat-sensitive.
The use of irreversible coloring agents to prevent tampering suffers from a number of disadvantages. Lottery tickets using irreversible color changes are subject to a relatively high number of "false voidings". An unintended color change due to accidental exposure to a chemical or to heat can result in a valid ticket being rendered invalid. In addition, irreversible inks generally require pretreatment of the paper substrate which adds to the cost of producing the lottery ticket.
Another approach to securing a scratch off lottery ticket is disclosed in Gilbert Bachman, U.S. Pat. No. 4,241,942. The lottery ticket employs a patterned layer of material to render visually hidden indicia on the ticket indistinguishable to a photocopy machine. The patterned layer renders any light rays which may be transmitted from the indicia to the paper of the photocopy process indistinguishable from the light rays transmitted from the patterned layer to the paper. As a result, the image which appears on the photocopy does not disclose the hidden indicia.
Fluorescent inks have also been used to prevent counterfeiting because the colors are not readily reproducible. For example, Herbert Laxer, U.S. Pat. No. 3,886,083 discloses a soluble and bleachable dye in combination with a fluorescent pigment whose fluorescence is enhanced if an alteration is attempted.
Anthony LaCapria, U.S. Pat. No. 4,066,280 discloses a document which has two overlapping but non-registering imprints. One of the imprints can be reproduced by a photocopier. The other imprint is from an ink including a specularly reflective opaque coloring material which partially masks a fluorescent material. The fluorescent material cannot be reproduced by a copier so that any attempt to photocopy the original ticket will fail to produce an exact duplicate.
All of the above mentioned methods of deterring the production of counterfeit tickets are disadvantageous because they are subject to false invalidations, require pretreatment of the substrate and/or do not provide a convenient means for on-site authentication of a winning ticket. A lottery ticket which can be rapidly and accurately authenticated by the retail agent would enhance lottery sales and improve the integrity of the lottery system.
All of the advantages would likewise be beneficial for the printing of negotiable instruments in which on-site authentication is of critical importance.